This invention relates to an improved piston pump of the kind which comprises a pump house, a rear cover and a bearing housing. The pump house is provided with axial borings passing through the house and these borings house each a piston which is biassed by a spring and axially movable by the influence of a rocker disk being rotatingly fastened to a shaft. The rear cover is provided with a circular distribution channel for a hydraulic liquid and connection borings leading to the piston borings for feeding hydraulic liquid thereto, said piston borings being in communication with an outlet channel for the pressurized hydraulic liquid through borings in the cylinder block.
Piston pumps of this kind are used among other things to control cranes e.g. on trucks. The development in this technological field has required an ever increasing pressure and a more rapid function than could be obtained by hitherto known constructions. The subject invention has for its purpose also to minimize the number of parts of the pump such that the wearing is reduced and further the pump is made less complicated and less expensive in manufacture.
According to the invention there has been achieved a piston pump of the kind referred to hereabove which in order to eliminate the recited drawbacks is characterised thereby that arranged in the inlet to the piston boring is a suction valve, this valve comprising a washer which is pressed into the piston boring and which serves as a valve seat, and a valve disk pressed against said washer by a spring as well as a valve guide, this guide being pressed by the spring, acting on the piston, against the washer thereby that a second valve washer by a spring is pressed against the outlet of the connection channel to the outlet of pressurized hydraulic liquid, said second spring housed in a boring in the rear cover and guiding said second valve disk by cooperation with a pin on said second valve washer so as to shut last-mentioned boring, the rear cover being somewhat conically shaped at its surface turned against the block such that its central area will be pressed with the highest force against the end surface of the block.
In the piston pump according to the present invention there is thus not used any balls in the valves as in previous constructions, such balls causing drawbacks in having a higher mass than washers and disks and therefore reacting more slowly. Balls also act against valve seats with smaller surfaces than washers and disks with obvious drawbacks.